The present application claims priority to Japanese Patent Application of Ikeda et al., filed Apr. 2, 2002, under No. 2002-099965, and Japanese Patent Application of Kato et al., filed Apr. 12, 2002, under No. 2002-111057, the entirety of each is hereby incorporated into the present application by this reference.
1. Field of the Invention
The present invention relates to an airbag used in a head protecting airbag device to be mounted on an automobile. Specifically, an airbag according to the present invention comprises an airbag body, and a tearable wrapping material for keeping the airbag body in a folded state. The airbag body is folded and housed in the peripheral edge of an opening at the interior side of a vehicular body, and expands and inflates so as to cover the vehicle""s interior side of the opening when inflation gas flows thereinto. After folding, the airbag body is wrapped by the wrapping material.
2. Description of Related Art
As disclosed in Japanese Patent Laid-Open No. Hei 11-321532, in the airbag for the head protecting airbag device of this kind in the prior art, a folded airbag body is wrapped by a wrapping material such as a tape member to keep itself in a folded state. Without this wrapping material, the airbag body, after being folded up, returns to the unfolded state and loses its folded-up configuration because of spring-back mechanism. Then the airbag body becomes bulky so that it cannot be mounted on the vehicle.
The wrapping member in the prior art was wound around the airbag body as folded into a generally rod-like shape, along the axis"" circumferential direction so as to intersect the axial direction of the airbag body perpendicularly. The folded airbag body was wound at several positions intermittently along its axial direction.
In the airbag in the prior art, more specifically, the portions wrapped by the wrapping member and the portions not wrapped are arranged alternately along the airbag body""s axial direction in the wrapping area. This inevitably leaves the portions not wrapped bulging due to the spring-back. Here arises a difficulty in housing the airbag body in a narrow housing portion when mounting on a vehicle.
Here, it is conceivable to wrap the airbag body with a bag-shaped (or cylindrical) wrapping member so that the airbag body may keep its folded-up configuration over its generally entire length. In this case, however, it would be troublesome to insert the folded airbag into the wrapping member if the wrapping member has a small diameter. If the wrapping member has a sufficient diameter, the diameter needs to be reduced after inserting the folded airbag body into the wrapping member. This work has to be applied over the entire length of the airbag body, which is troublesome, too.
Moreover, the smooth expansion and inflation from the wrapped state also needs to be considered as well as compact-wrapping of the airbag body.
The present invention contemplates to solve the above-specified problems, and therefore, its object is to provide an airbag which is capable of keeping the airbag body in the wrapping area in a compact shape by a simple wrapping work, while securing a smooth expansion and inflation.
The first airbag according to the present invention comprises an airbag body and a tearable wrapping member for keeping the airbag body in the folded state. The airbag body is folded and housed in the opening peripheral edge at the interior side of a vehicular body. The airbag body is wrapped by a wrapping member after being folded in such a manner as to expand and inflate to cover the opening when the inflation gas flows thereinto. The wrapping member is constructed of a plurality of wrapping yarns having flexibility. The plurality of wrapping yarns are wound around the airbag body as folded into a generally rod-like shape over the generally entire length in the wrapping area, along the airbag body""s axial direction, and in a manner to obliquely intersect the axial direction. At least two of the wrapping yarns are wound around the folded airbag body in the wrapping area from the opposite directions. The distance between the adjacent yarns along the axial direction of the folded airbag body, with respect to the wrapping yarns wound in the same direction in the wrapping area, is within the range of 20 to 60 mm, when the wrapping yarns are wound around the folded airbag body. The yarn strength of these wrapping yarns according to JIS L 1013.7.5 is within the range of 7.4 to 65N.
In the first airbag according to the present invention, a plurality of wrapping yarns constituting the wrapping member are not arranged intermittently, but wound around the folded and rod-shaped airbag body along the axial direction of the airbag body, and in a manner to intersect the axial direction of the airbag body obliquely, in the wrapping area of the airbag body. Moreover, at least two of the wrapping yarns are wound around the folded airbag body from the opposite directions.
In the first airbag according to the present invention, accordingly, most part of the outer circumference around the airbag body is held by the wrapping yarns at more than one positions in the wrapping area. As a result, the compactly folded state of the airbag body is uniformly kept along the axial direction of the airbag body. More specifically, even with only two wrapping yarns, those yarns are wound around the folded airbag body in the opposite directions. In this case, two yarns hold the outer circumference around the airbag body only at one position by their intersection. However, in the portion between the intersections apart from the intersection, two yarns are separated from each other to hold the outer circumference of the airbag body. Therefore, the airbag body is wrapped compactly.
Moreover, the wrapping work can be made easily by winding a plurality of wrapping yarns generally helically around the airbag body so as to intersect the axial direction of the airbag body obliquely.
Especially in the present invention, a plurality of wrapping yarns are wound around the folded airbag body, while the distance between the adjacent yarns along the axial direction of the folded airbag body is within the range of 20 to 60 mm, with respect to the wrapping yarns wound in the same direction. Moreover, the yarn strength of the wrapping yarns according to JIS L 1013.7.5 is within the range of 7.4 to 65N. Therefore, the airbag body is wrapped compactly without degrading the expanding property of the airbag.
More specifically, if the distance between the adjacent yarns is less than 20 mm, the density of the wrapping yarns per unit length along the axial direction of the airbag body becomes high. Then the resistance in breaking the wrapping yarns becomes big when the airbag body breaks the individual wrapping yarns to expand and inflate, which is likely to delay the expansion of the airbag. On the contrary, if the distance between the adjacent yarns is more than 60 mm, the area of the airbag body not held by the yarns enlarges in the axial direction of the airbag body, and therefore, the area is likely to bulge, which checks the effect of the present invention of wrapping the airbag body compactly.
Therefore, it is desired that the distance between the adjacent yarns along the axial direction of the folded airbag body, with respect to the wrapping yarns wound in the same direction, be set within the range of 20 to 60 mm.
Moreover, if the yarn strength of each wrapping yarn according to JIS L 1013.7.5 is less than 7.4N, the wrapping yarn is torn when the wrapped airbag body is bent, and fails to wrap the airbag body compactly. On the contrary, if the yarn strength of each wrapping yarn according to JIS L 1013.7.5 is more than 65N, the resistance in breaking the wrapping yarns becomes big when the airbag body breaks the individual wrapping yarns to expand and inflate, which delays the expansion of the airbag.
From the above-described viewpoints, it is desired that the yarn strength of the wrapping yarns according to JIS L 1013.7.5 be within the range or 7.4 to 65N, or within the range of 18.7 to 41N, more desirably.
Therefore, in the first airbag according to the present invention, the airbag body in the wrapping area is kept in a compact shape by a simple wrapping work while securing a smooth expansion and inflation. Moreover, the airbag body keeps its compact shape even if the airbag body is bent after being wrapped.
The wrapping yarns in the wrapping area are wound around the folded airbag body at the intersection angle of 45xc2x0 or more with respect to the axial direction of the folded airbag body. With this construction, the airbag body is further prevented from loosing the folded-up shape even if the wrapped airbag body is bent.
More specifically, when the wrapped airbag body is bent at approximately 180xc2x0 and is returned, the part of the airbag body between the adjacent yarns in the vicinity of the bent point is likely to get out of the folded state, thereby causing the portion of the bent outer circumference to protrude partially. This is because the wrapping yarns near the bent point are shifted in the direction generally perpendicular to the axial direction of the airbag body, so that the yarns become parallel to the axial direction of the airbag body. Then the part of the airbag body protrudes from the space between the wrapping yarns. This protruded portion is likely to remain protruded even if the bending is returned thereafter, since the protruded portion comes to be clamped by the wrapping yarns.
Especially, if the intersection angle between the wrapping yarns in the wrapping area and the axial direction of the folded airbag body is less than 45xc2x0, the intersection angle with the airbag body axial direction is shallow. Accordingly, when the airbag body is bent at approximately 180xc2x0, the wrapping yarns near the bent point are easily shifted in the direction generally perpendicular to the axial direction of the airbag body, so that the yarns may become parallel to the axial direction of the airbag body. Then a big protruded portion is formed in the portion between the wrapping yarns. As a result, when the wrapped airbag body is housed in a vehicle, the airbag body cannot be smoothly housed in a predetermined housing portion since the protruded portion engages surrounding members. Here, the intersection angle is less than 90xc2x0.
If more than six wrapping yarns are used, many yarns remain untorn and help keep the airbag body in a folded state even when one wrapping yarn is torn.
Moreover, it is desired that the extension of the wrapping yarns according to JIS L 1013.7.5 be set within the range of 10 to 30%.
If the extension is less than 10%, the extension is small. With the small extension, many of the yarns are torn when the wrapped airbag body is bent, thereby allowing the airbag body to get out of the folded state. If the extension is 10% or more, less yarns are torn when the wrapped airbag body is bent. Then the wrapped airbag body can be handled in a bent and compact state, without collapsing the folded configuration, thereby facilitating the transfer and control until being mounted on a vehicle.
If the extension exceeds 30%, on the contrary, the extension is too big. With the big extension, a plurality of wrapping yarns are liable to stretch and gather when the airbag body expands and inflates. Then the wrapping yarns partially get together like one string of yarn and obstruct the expansion of the airbag body at the portion, which delays the expansion and inflation of the airbag as a whole.
Moreover, when the airbag body is provided at the upper edge thereof in the wrapping area with mounting portions for mounting the airbag body on a vehicle, the winding pitch of the wrapping yarns in the vicinity of the mounting portions may be widened compared with other portions. With this construction, the mounting portions can be taken out easily after the wrapping work, since they are not held tightly by the wrapping yarns.
The second airbag according to the present invention comprises an airbag body and a tearable wrapping member for keeping the airbag body in the folded state. The airbag body is folded and housed in the opening peripheral edge at the interior side of a vehicular body. The airbag body is wrapped by a wrapping member after being folded in such a manner as to expand and inflate to cover the opening when the inflation gas flows thereinto. The wrapping member is constructed of a plurality of wrapping yarns which braid-wrap the airbag body as folded into a generally rod-like shape, along the airbag body""s axial direction, and in a manner to obliquely intersect the axial direction. The airbag body includes a wrapping area which is wound by the wrapping yarns in a braiding fashion, and is prevented from getting out of the folded up configuration. The wrapping area has a tied portion which is formed by winding the wrapping yarns braiding at the ends of the wrapping area without moving the yarns in the axial direction of said airbag body, for preventing the wrapping yarns from loosening.
In the second airbag of the present invention, too, a plurality of wrapping yarns constituting the wrapping member are not arranged intermittently, but wound around the folded and generally rod-shaped airbag body in a braiding fashion, along the axial direction of the airbag body, and in a manner to intersect the axial direction of the airbag body obliquely, in the wrapping area of the airbag body.
In this braid-wrapping, a plurality of wrapping yarns are divided into two groups, and the yarns of the individual groups wind the folded airbag body from the opposite directions to each other. Moreover, one yarn disposed over the other yarn on the outer circumference of the airbag body at an intersection of the wrapping yarns, is alternately disposed below the other yarn at another intersection on the extension line of the same yarn along the axial direction of the airbag body. Further at yet another intersection, the yarn holds another yarn. In the braid-wrapping, the holding and held states are thus repeated.
In the second airbag of the present invention, therefore, most part of the outer circumferential sides around the axis of the airbag body in the wrapping area are held by the wrapping yarns at more than one portion. As a result, in the wrapping area, the compactly folded state of the airbag body is kept uniformly along the axial direction of the airbag body, as in the first airbag. Specifically, even with only two wrapping yarns, those yarns are wound around the folded airbag body in the opposite directions. In this case, two yarns hold the outer circumferential side around the airbag body only at one position by their intersection. However, in the portion between the intersections apart from the intersection, two yarns are separated from each other to hold the outer circumferential side of the airbag body. Therefore, the airbag body is wrapped compactly in the wrapping area.
The wrapping work is simply done by winding the wrapping yarns in a braiding fashion around the airbag body so that the wrapping yarns may intersect the axial direction of the airbag body obliquely. Therefore, the wrapping work can be done easily by utilizing a device similar to a braiding machine used in forming a braided layer of a reinforced hose having a braided layer, for example.
At the end of the wrapping area, moreover, the wrapping yarns are prevented from loosening by a tied portion which is formed by winding and tying the wrapping yarns braiding without moving the wrapping yarns in the axial direction of the folded airbag body. Additional treatments such as retaining with a tape member are not necessary with respect to the end treatment of the wrapping yarns at the end portions of the wrapping area. Therefore, the end treatment of the wrapping yarns can be made easily.
Especially in the second airbag of the present invention, the wrapping yarns in plurality wrap the airbag in a braiding fashion. In this braiding fashion, as afore-described, a wrapping yarn holds the other yarn at an intersection, and is held by another yarn at another intersection along the axial direction of the folded airbag body. Therefore, if the wrapping yarns are wound around the airbag body once or more with the transfer merely stopped, without moving the winding position, the yarns hold and bind one another to form a tied portion easily for preventing the individual yarns from loosening.
In the second airbag of the present invention, therefore, the airbag body in the wrapping area is kept in a compact shape by a simple wrapping work, and the end treatment at the end portion of the wrapping area, for preventing the loosening of the wrapping yarns, is made easily. Therefore, the airbag wrapped can be manufactured with less work and at low cost.
Of course, if the wrapping yarns are braid-wrapped twice or more at the tied portion, the yarns are further tied tightly one another.
When the airbag body includes at least two front and rear wrapping areas as separated longitudinally, and is provided with the tied portions at the adjacent end portions of the front and rear wrapping areas, the wrapping yarns may be connected along the axial direction of the folded airbag body, in the portion of the airbag body between the adjacent tied portions of the front and rear wrapping areas. With this construction, the following working-effects are obtained.
If the airbag body includes more than one wrapping areas, specifically, the braiding work can be done without cutting the wrapping yarns, but with the yarns connected, between the adjacent tied portions of the wrapping areas. Therefore, the wrapping work can be done efficiently in each of the wrapping areas. At this time, there is no need to wind the wrapping yarns around the folded airbag body at the portion between the tied portions of the adjacent wrapping areas. Instead, the airbag body has only to be moved forward. Therefore, a plurality of wrapping areas are wrapped easily.
In this case, a joint mouth portion may be provided in the portion of the airbag body between the front and rear wrapping areas as separated longitudinally. The joint mouth portion is to be connected to the inflator for supplying the inflation gas, and to introduce the same into the airbag body.
With this construction, at the portion of the airbag body between the front and rear wrapping areas as separated longitudinally, the wrapping yarns in plurality are merely extended along the axial direction of the folded airbag body. Therefore, the joint mouth portion can be easily extracted from the gap between the predetermined wrapping yarns, to be connected to the inflator smoothly.
Of course, a mounting portion may be provided at the portion of the airbag body between the front and rear wrapping areas as separated longitudinally for mounting the airbag body on a vehicular body. With this construction, a mounting portion can be mounted on a vehicular body easily.
Furthermore, a tearable tape member may be wound around the tied portions at the front and rear ends of the airbag body. With this construction, although it is anticipated that the vicinity of the end side tied portions at the front and rear end side of the airbag body may loosen in relation with surrounding members in the course of handling such as the transfer, the tape member prevents the loosening of the wrapping yarns. Even if the tearable tape member is wound around these portions, the working-effects of the present invention are not remarkably decreased compared with the conventional wrapping manner of winding tape material intermittently, since the number of the winding portions is reduced.